Consider two algebraic spaces \(U,V\)  with a regular function \(f:U\rightarrow \mathbb {C},g:V\rightarrow \mathbb {C}\) , denote by \(k:U_0\times V_0\rightarrow (U\times V)_0\)  the embedding into the zero locus of \(f\boxplus g\) . Massey defines in [1]} a natural Thom-Sebastiani isomorphism:
\(\phi _f\boxtimes \phi _g\simeq k^\ast \phi _{f\boxplus g}\) 
